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Details for Benchmark: JC1175

N 38° 40.233 W 090° 11.333 (NAD 83)

Altitude: 430.34

Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)

Location:
In C OF ST LOUIS county, MO View Original Datasheet
Designation:
K 323
Marker Type:
metal rod
Setting:
stainless steel rod
Stability:
Probably hold position/elevation well.

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I did not find JC1175. I did not find a witness post.
There are a multitude of survey marks in that area though. I did find an Army Corps of Engineers' benchmark disk in the top of the floodwall to the South of where JC1175 should be.
I could not find a designation nor a date on this COE disk.

[Photos:]
photoCOE mystery disk
found to the South of where JC1175 should be. (Lat & lon from my recreational handhelp Magellan GPS at the COE disk.)
photoanother view of the COE disk

Documented History (by the NGS)

01/01/1981 by NGS (MONUMENTED)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1981 IN ST LOUIS. IN ST LOUIS, 0.3 KILOMETER (0.2 MILE) SOUTH ALONG TOP OF THE LEVEE AND FLOOD WALL OF THE MISSISSIPPI RIVER FROM THE CROSSING OF THE MERCHANTS BRIDGE, 9.54 METERS (31.3 FEET) WEST OF THE WEST FACE OF THE FLOOD WALL, AND 0.43 METER (1.4 FEET) NORTH OF A METAL WITNESS POST. THE MARK IS 0.43 METERS S FROM A WITNESS POST. THE MARK IS ABOVE LEVEL WITH LEVEE.
03/26/1991 by USPSQD (MARK NOT FOUND)
RECOVERY NOTE BY US POWER SQUADRON 1991 (DWS) MARK NOT FOUND.

Control Text

  • The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds.
  • The orthometric height was determined by differential leveling and adjusted by the National Geodetic Survey in June 1991.
  • The geoid height was determined by GEOID99.
  • The dynamic height is computed by dividing the NAVD 88 geopotential number by the normal gravity value computed on the Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 degrees latitude (g = 980.6199 gals.).
  • The modeled gravity was interpolated from observed gravity values.

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